GB2500997A - Load lifting device with gas strut and extendible support means - Google Patents

Abstract

Load lifting device 10 with platform 18, extendible support means 16 and at least one gas strut 30. The actuation means 24 for enabling extension of the support means 16 may be a pulley system (figure 5), which may be manually operable. The at least one gas strut 30 may tend to urge the support means into its extended position, and may be located within the support means. There may be two gas struts 30, 30 fixed relative to one another, and engaging in a common guide means 31. The support means may be vertically extendible, potentially comprising at least two elements, which may be concentrically nested housings 20, 22, linearly slidable relative to each other in telescopic manner. A portion of the actuation means 24 may be permanently fixed to one of the housings 20, 22 and to the platform 18. Figures 12 and 13 show an alternate embodiment using a scissor lift.

Description

Title: Load Lifting Device

Field of the invention

This invention relates to a load lifting device.

Background to the invention

Load lifting devices come in a variety of different forms often providing a fiat working platform suitable for canying a load which is raisable to different heights.

This allows ready access to elevated regions, for example when stacking shelves in a i o warehouse.

When heavy loads are raised to a height, large amounts of power arc required to lift the platform and load, whether power from a motor or from manual effort.

It is an aim of the present invention to reduce the power needed for raising such loads.

Summary of the invention

In accordance with the present invention, there is provided a load lifting device comprising a platform fixed to an extendible support means for raising and lowering the platform, wherein at least one gas strut is associated with the extendible support means and an actuation means is associated with the support means, the actuation means operable to enable extension of the support means. The gas strut reduces the force needed to operate the actuation means as the gas strut will at least partially counteract the weight of the platform and any load carried by it.

The gas strut may be located within the extendible support means, the gas strut acting to urge the support means to an extended position. This can be used where load lifting devices are used to access elevated areas, for example using booms that travel through an arc or with the support means preferably extending vertically.

The actuation means, or actuation system, may be electrically powered, for example by batteries or be manually operable as such load lifting devices are often used in environments without ready access to electricity.

I

The support means preferably comprises at least two elements linearly slidable with respect to each other.

Preferably the support means comprises an inner and outer housing, the inner housing nestable within the outer housing. When the support means is in an unextended position, the inner housing will fully nest within the outer housing. As the actuation means is operated and the support means extends, the inner and outer housings move relative to each other with the gas strut urging against the outer housing so as to a partially support the mass of the platform and the associated load. Typically the inner housing will be static, the outer housing moved relative to the static inner housing.

The actuation means may be provided by a lead screw system or equivalent and in particular the actuation means may comprise a pulley system which is of advantage as it is robust, simple to use and inexpensive. A pulley system may utilise belts, toothed belts, chains, wire ropes and the like.

A portion of the actuation means may be permanently fixed to at least one housing so that operation of the actuation means moves the housings relative to each other.

Where the actuation means comprises a pulley system, a drive loop, such as a belt is preferably located within the outer housing and external to the inner housing, and is permanently fixed to the inner housing so that the inner housing moves in response to movement of the belt.

Where such a pulley system is for linearly slidable elements, the pulley system comprises a drive band fixed with respect to one of the elements and passing around at least two pulley wheels fixed with respect to the other element.

If desired, two gas struts may be used and located within the support means, held in a fixed relationship to each other to act along a common axis, typically a vertical axis.

In such an arrangement an end of one strut will act on one end of the second strut.

Each gas strut may engage with a common guide means, the guide means acting as an interface between the gas struts, controlling positioning of the gas struts within the support means.

The invention will now be described, by way of example, and with reference to the accompanying drawings in which: Figure 1 shows, in accordance with the present invention, a side view ofa load lifting device including a support mast; Figure 2 shows a cross-section through the support mast along line 11-11; a Figure 3 shows plan and side views of a guide means used within the support mast; Figure 4 shows a cross-section through the support mast when partially extended; Figure 5 shows a partial internal vicw of the support mast showing details of a pulley system; Figure 6 shows a detailed view of part of a mechanism used to operate the load lifting device; Figure 7 shows a detailed view of part of the pulley system; Figure 8 shows partial extension of the support mast; Figure 9 shows a cross-section through the support mast when partially extended; Figure 10 shows a simplified partial view from the front of the load lifting device when fully extended; Figure 11 shows a cross-section through part of a modified support mast; and Figures 12 and 13 show an alternative embodiment.

Description

Figure 1 shows a mobile load lifting device 10 comprising base 12 to which are attached four wheels 14 and upright support or mast 16 to which is affixed elevatable work platform 18. Support 16 comprises nested inner and outer housings 20, 22, moveable relative to each other by attached pulley mechanism 24 when operated by external crank handle 26. A protective cover 28 prevents items being inadvertently trapped in pulley mechanism 24. Inner and outer tubular housings 20, 22 are typically made from steel and are hollow with a rectangular cross-section. Outer housing 20 is closed at its uppermost end by face 29 whereas inner housing 20 is open at both ends so that two co-operating gas struts 30, 30' located centrally within inner housing 20 urge against face 29 and base 12. The two gas struts 30, 30' are fixed with respect to each other by securing to a guide means in the form of wheeled trolley 31 Guide wheels 32, 33 are located on the external face of inner section 20 and the internal face of outer section 22 respectively so as to guide the sections 20, 22 as they move relative to each other.

Pulley mechanism 24 comprises fixed pulley wheels 34, 36 located on an inner face of outer housing 22, see Figure 5, so as to be contained in a void 37 between the two housings and both wheels 34, 36 fixed with respect to outer housing 22. Toothed a drive belt 38 made from polyurethane passes around wheels 34, 36 and is fed bctwccn drive cog 40 and guide wheel 41 pivotally located on housing 22. Attachment 42 is bolted to inncr housing 20 and sccurcs to drivc belt 38 to pcrmancntly fix bclt 38 to housing 20.

Drive cog 40 is attached to crank handle 26 by way of bearing block 44 and spur gears 46, 48, see Figure 6 and also Figure 2 which shows a cross section through mast 16 when crank handle 26 is in a horizontal position. Spur gear 48 and drive wheel 40 are on a common shaft.

Figure 3 shows trolley 31 in detail, with a plan view shown in Figure 3(a) and a side view in Figure 3(b). Trolley 3 1 comprises two elongate arms, 50, 52 overlapping centrally to form a cruciform shape. An end of each arm carries an axle bearing a pair of wheels 54. A central threaded aperture 56 receives onc end of each gas strut 30, 30', securing the gas struts with respect to cach other and with rcspcct to trolley 31.

Trolley 3 1 is configured so that wheels 54 are able to travel along the internal diameter of housing 22 and so guide vertical movement of struts 30, 30', see Figure 4.

Trolley 31 freely rolls up and down the internal face of housing 20 with minimal resistance ensuring gas struts 30, 30' are correctly aligned as mast 16 telescopes upwards or retracts downwards, and prevents struts 30, 30' buckling during downward movement as it enables shorter length more robust gas struts to be used in combination along a common axis to achieve the required maximum extension.

Where a single larger gas strut is used instead of multiple gas struts, trolley 31 can be located near the mid-region ofthe single strut to provide support and prevent buckling when the gas strut is fully extended.

Figures 5 and 7 show the load-lifting device in its unextended position as in Figure 1 where inner housing 20 is fully nested within outer housing 22. If a user desires to raise work platform 18, then they turn handle 26 in a clockwise direction to drive small spur gear 46 which in turn drives larger spur gear 48 connected to drive cog 40.

Spur gears 46, 48 reduce the effort needed to turn handle 26 but also reduce travel a speed at pulley wheels 34, 36. Drive cog 40 turns in response to movement of gear 48 to move drive belt 38 and due to the permanent attachment of inner housing 20 to a fixed point on belt 38, inner housing 20 moves relative to outer housing 22, outer housing 22 extending vertically upwards, see Figures 8 and 9. Figure 9 shows an embodiment using a single gas strut but generally two gas struts with a supporting trolley will be used to avoid buckling of the single gas strut during downward movement and to reduce production costs.

Pressurised gas strut 30 which can be seen in Figure 1 but is omitted in the views of Figures 5, 7 and 8 for clarity, continually urges against face 29 of outer housing 22, with an upper end of gas strut 30' urging against the base of trolley 31. Gas struts 30, 30' are permanently attempting to extend but can only extend as and when inner housing 20 moves relative to outer housing 22. When the two housings extend, the mass of work platform 18 and any payload it is cariying arc partly supported by the force from gas struts 30, 30'. This significantly reduces the amount of force that a user or motor needs to apply to crank handle 26 to move housings 20, 22 relative to each other and to raise platform 18 vertically.

When attachment fixing 42 reaches wheel 36, inner housing 20 has reached its maximum distance of travel with regard to housing 22 and at this point a maximum travel of around 1200mm has been achieved, see Figure 10. As will be readily apparent to those skilled in the art, by adjusting the lengths of the telescopically nested housings and drive belt 38, greater or lesser distances of travel can be achieved for work platform 18.

Once the maximum extent has been reached, a user will turn crank handle 26 in an anti-clockwise direction to reverse the travel of belt 38, retract the two housings 20, 22, and so lowcr platform 18.

If desired, the pulley system can be operated by a powered drive but a manually operated drive can be of use where electricity is not readily available. The gas strut assists raising of the platform requiring less energy to lie used either by an operator or by a motor. Equivalent systems of chain drives, wire rope systems can be used to io move the housings relatiye to each other.

Whcrc necessary, the slidabic housings with internal supporting gas struts can be combined with additional nested housings to provide a loilger telescopic mast to which the elevatable work platform 18 is attached. Thus as shown in Figure 11, additional tubular scctions 60, 62 having successively increascd diameters ovcr scction 22 are providcd to cxtcnd the maximum hcight achicvable for platform 18.

When in a fully lowered position, sections 20, 22 and 60 nest within section 62.

Section 62 typically has a scaled end portion 63. Third and fourth mast sections 60, 62 are moveable relative to second mast section 22 by pulley system 64 comprising belt 66 routed through fixed pulley wheel 68 attached to mast section 60 and fixed pulley wheel 70 attached to mast section 22. Belt 66 is secured at one end to end portion 63 of mast section 62, and the other end of belt 66 is secured to rim 71 of section 62. Drive cable fixing 72 acts as a stop dcfining thc fully raiscd position of sections 60 aild 62. As with sections 20, 22 shown in Figure 1, gas springs can be located between the third and fourth sections 60, 72 or a plurality of interconnected gas springs can be fitted in the centre of the mast sections, typically with connecting wheeled trolleys 31 between adjacent gas struts.

If desired the invention can be used with a boom or V' lift mechanism 80 as shown in Figures 12 and 13. V' lift 80 comprises base 82 to which is attached a plurality of connected pivotable booms 86, 90 moveable about pivots or knuckles 88, 92 and 94 to adjust the vertical heights of working platform 96. Pulley wheel 94 attached to an end of boom 90 furthest from pivot 92 bears a working platform 96. Rotating lowest knuckle 88 causes a tension line (not shown) in knuckle 92 to raise boom 90 so adjusting the height ofplatlbrm 96. In a non-elevated position, booms 86 and 90 are substantially parallel to the horizontal surface of base 82.

s In accordance with the invention, gas strut 100 is attached to base 82 and lower support 86. As with the first embodiment gas slrut 100 urges against lower support 86 so as to reduce the force needed to raise support 86 as it rotates around pivot 88 to raise platfbrm 96. If desired, pulley system 110 is combined with gas strut 100 with pulley system 110 comprising pulley wheels 114, 118, 120 located adjacent pivots 88, 92 and 94 and an additional pulley 112 located on work platlbrm 96. Drive belt 116 extends from pulley wheel 112 down to base 82 through pulley wheels 114, 118 and 120. Manual rotation of handle 122 connected to pulley 12 moves belt 116 causing the supports 86, 90 to adjust their position relative to the horizontal and so elevate or lower platform 96 with gas strut 100 urging against support 86 and reducing the load is required to operate pulley system 110. Typically clockwise movement of handle 122 will lower platform 96 and anticlockwise movement will raise platform 96. Tf desired, pulley system 110 can be electrically operated.

Claims (13)

1. Claims 1. A load lifting device comprising a platfbrm fixed to an extendible support means, wherein at least one gas strut is associated with the extendible support means and an actuation means is s associated with the support means, the actuation means operable to enable extension of the support means.
2. 2. A load lifting device according to claim 1, wherein the at least one gas strut acts to urge the support means to an extended position.
3. 3. A load lifting device according to claim 1 or claim 2, wherein at least one gas strut is located within the support means.
4. 4. A load lifting dcvicc according to claim 1, wherein the support means is vcrtically is extendible.
5. 5. A load lifting device according to any of the preceding claims, wherein the actuation means is manually operable.
6. 6. A load lifting device according to any of the preceding claims, wherein the support means comprises at least two elements linearly slidable with respect to each other.
7. 7. A load lifting device according to any of the preceding claims, wherein the support means comprises an inner and outer housing, the inner housing nestable within the outer housing.
8. 8. A load lifting device according to any of the preceding claims, wherein the actuation means comprises a pulley system.
9. 9. A load lifting device according to any of the preceding claims, wherein a portion of the actuation means is permanently fixed to at least one housing.
10. 10. A load lifting device according to any of claims I to 8, wherein a portion of the actuation mechanism is permanently attached to the platfbrm.
11. 11. A load lifting device according to any of the preceding claims, wherein two gas struts are located within the support means, the gas struts being held in fixed relationship to each other to act along a common axis.s
12. 12. A load lifting device according to claim 7, wherein each gas strut engages with a common guide means controlling positioning of the gas struts within the support means.
13. 13. A load lifting device substantially as herein described with reference to and as illustrated in the accompanying drawings.